Re: panic: kmem_malloc(131072): kmem_map too small (AMD64)

On Mon, Sep 24, 2007 at 08:04:33AM -0500, Larry Rosenman wrote:
> On Mon, 24 Sep 2007, Kris Kennaway wrote:
> 
>> Ruslan Ermilov wrote:
>>> On Sat, Sep 22, 2007 at 11:37:37PM +0200, Kris Kennaway wrote:
>>>> Darren Reed wrote:
[...]
>>>>> Stupid question, perhaps, but is vm.kmem_size/vm.kmem_size_max limited 
>>>>> by physical RAM?
>>>> Yes.
>>> To be precise, it's actually limited by 2 * sizeof(physical RAM).
>>> It's still size of a _virtual_ memory map (kmem_map), after all:
>>> :	/*
>>> : 	 * Limit kmem virtual size to twice the physical memory.
>>> : 	 * This allows for kmem map sparseness, but limits the size
>>> : 	 * to something sane. Be careful to not overflow the 32bit
>>> : 	 * ints while doing the check.
>>> : 	 */
>>> : 	if (((vm_kmem_size / 2) / PAGE_SIZE) > cnt.v_page_count)
>>> : 		vm_kmem_size = 2 * cnt.v_page_count * PAGE_SIZE;
>> 
>> Well OK, but that seems pretty dangerous, because it leaves open a pathway 
>> to exhaust all of physical memory and presumably panic.
> 
> is KVA pageable?  Is the kmem_map dedicating non-pageable memory?
> 
kmem_map is used to map memory for the zone allocator, including
malloc(9).

> I've set my vm.kmem_max to 1G, (on a 4G amd64 box).  Is that reasonable?
> 
It just means that your kernel can "malloc" up to 1G of memory.


Cheers,
-- 
Ruslan Ermilov
ru_at_FreeBSD.org
FreeBSD committer